The present invention relates to apparatus for capturing digital images of pages of a book in a manner which is extremely gentle to the pages and binding thereof and which is of high resolution and is distortion free. This apparatus has particular utility for archiving digital images of rare and fragile books which curators of such collections are reluctant to have manipulated.
There exists a major effort among large libraries and museums around the world to preserve bound volumes in digital form in order to capture and preserve for posterity books which are in an increasing state of natural decay. Millions of books are so rare and priceless that only very few people are allowed to handle or even view the volumes. Many others printed widely about 100 to 200 years ago on acid paper are decaying rapidly and are becoming extremely fragile. Therefore, a major challenge is to capture the information contained therein, in digital form, before it is too late, so that it may easily be reproduced and printed, and this body of knowledge may be brought to the public at large. To this end, high quality images of billions of pages must be captured in a relatively short period of time, in a manner which will not adversely impact the physical well being of each book.
Although a number of approaches have been taken to accomplish bound volume imaging, none have been gentle enough to satisfy rare book curators and librarians that harm will not befall their collections. One approach is to capture page images while the book is lying flat upon a support, with its pages facing upwardly. Pages of books lying in this position will have a curvature in the region of the spine, which will distort the captured images. Therefore, provision must be made for either rendering them relatively flat by means of a pressure plate or, alternatively, capturing distorted images and then correcting them by means of appropriate correction software. In either case, this approach is unacceptable because the bindings of fragile books will be damaged by opening them to 180xc2x0.
Another approach is to provide a copier machine with a book supporting platen. This entails placing the book with its pages facing downwards upon the platen, which may be wedge-shaped to reduce the extent of opening the book, thus protecting its spine. When supported in this manner, both pages are imaged, either sequentially or simultaneously. Then the book is lifted and turned over so that the operator may turn its pages manually. Finally, the book is returned to the platen for further imaging. Clearly, this is an unacceptable technique for fragile books because the spine may be damaged by supporting the weight of the book and the constant manipulation will inevitably result in harm to the book.
Yet another approach is to provide a cradle to support a book in a partially open state and to introduce a wedge-shaped platen assembly between the pages for capturing page images, either simultaneously or sequentially. In order to turn pages, the cradle and wedge-shaped platen are relatively movable away from one another. In order to image the pages, these elements are driven towards one another. Suitable sensors are usually provided to insure a xe2x80x9csoft landingxe2x80x9d when the wedge-shaped platen contacts the book. Such totally mechanical systems have been found to be unacceptable for rare and fragile books because they rely on mechanically driven systems, which may destroy the books in the event of system malfunctions.
It is an object of the present invention to provide a mechanism which will have the lowest adverse impact on a fragile book, and yet will enable an operator to capture the highest quality images from robust as well as fragile bound volumes. To this end, the curator and librarian community, having responsibility for rare and fragile books, has insisted upon a mechanism which is wholly in the operator""s manual control and which will insure that a well trained operator""s tactile feedback will protect the integrity of even the rarest of books.
A further object of the present invention is to provide a manually operable mechanism which enables an operator to achieve perfect focusing and gentle contact with the book, while at the same time allowing the operator to reposition the relatively movable elements thereof in an easy and tireless manner. Such a mechanism will prevent operator fatigue, which would inevitably lead to damage of these priceless treasures.
These objects are accomplished, in one form, by the present invention which includes a book imager having a cradle for supporting a book, and an optical system positioned above the cradle. The optical system is mounted for movement along a vertical axis toward and away from the cradle. It includes an upper portion supporting a camera and mirror arrangement and a lower portion comprising a platen assembly. The upper and lower portions are mounted for independent movement along the vertical axis over a first range of travel remote from the cradle, and are coupled for movement as a single unit over a second range of travel, toward and proximate to the cradle. When the upper and lower portions are coupled, the optical system has a fixed focal length extending from the platen surface, through the mirror arrangement and through the camera.